The collection of post-consumer rigid plastic containers has recently begun. "Post-consumer" means that the consumers have used the contents of the containers and then disposed of them. The problem arises as to how to recycle these containers for beneficial purpose rather than dispose of them in landfill or by incineration. The term "recycle" means remelt-fabrication into useful articles, as distinguished from returning the container to the bottle for cleaning and refilling.
Solution to the problem faces serious obstacles. It has become convenient to "package" post-consumer rigid plastic containers as bales of crushed containers held together by strapping or other securement. The crushing of containers removes air from the inside of the containers and provides a densified mass which has economy in transportation and ease of handling. One obstacle to the recycling of these bales of containers is that the bales must be broken down in individual containers for recycle processing.
Difficulties in breaking down bales of crushed post-consumer rigid containers include the degree of compaction of the bales which varies at least from site-to-site where the baling is done, so that the debaling has to accommodate the different degrees of bale integrity. In addition, the crushed containers in the bales tend to stick to one another, either by physical interlocking caused by the crushing process and/or by adhesion caused by sticky residue of the contents of the containers and/or by cohesion between container surfaces forced together by the crushing process. One of the most common plastics used for rigid containers, i.e., polyethylene terephthalate (PET) is particularly susceptible to such cohesion.
Another obstacle arises from the content of the bales of crushed containers. The plastics content varies from bale to bale, i.e., the bales will generally contain a mixture of containers of different plastics, and the proportion of containers of particular plastics will vary from bale to bale. The composition of the bales will also vary from source to source. Curbside trash collection which includes rigid plastic containers segregated from the rest of the trash produces different mixtures from neighborhood to neighborhood and region to region. The same is true for the collection of post-consumer rigid plastic containers from separation activity carried out at regional centers such as material recovery facilities (MRFs) for the receipt of consumer trash. Bales concentrated in PET soda bottles may be obtained from deposit bottle collection points. The same is true of high density polyethylene (HDPE) milk and water bottles. The containers of still other plastics are commingled in varying proportions in these bales. Any recycle operation for post-consumer rigid plastic containers must be able to process bales of crushed containers from all these sources and of all compositions.
Another obstacle to the recycle of post-consumer rigid plastic containers is economics. The recycle plastics must have value in order for the recycle operation to succeed. The value of recycle plastics tends to be "capped" by the selling price of virgin resin of the same identity. Recycle plastic tends to have a lower value than virgin resin, because the recycle plastic may not be as good as the virgin resin, i.e, the physical properties of the virgin resin are may be degraded by the presence of post-consumer contaminants and/or the degradation that may occur in the remelting of the recycle plastic.
Heretofore PET soda bottles have been subjected to recycling, wherein a loose collection of these bottles were delivered to the recycling operations. These PET soda bottles included the HDPE base cup and label which are adhered to the PET bottle by glue, the label generally being either polypropylene film or paper. These bottles also included the cap retaining ring and sometimes even the bottle cap of aluminum or polypropylene. Sometimes, however, for ease of recycling, the base cup was removed by hand prior to feeding the PET bottle to the recycle operation. In this process operation, the feed was pure PET bottle in its original shape and free of dirt, trash and other contaminants, and the step of removal and separation of the PET portion of the bottle from the base cup and label contaminants was all that had to be solved technically and economically for a viable recycle process.
The problem of the recycle of post-consumer rigid plastic containers in the form of bales of varying composition of commingled crushed containers of different plastics has to be solved within the same economic framework, but now with the greater difficulties arising from this bale feed to the recycle operation. Typically, a bale of crushed post-consumer rigid plastic containers contains various plastics in the following approximate minimum amounts based on the total weight of the bale: 30 weight percent PET, 30 weight percent HDPE, 0.5 weight percent polyvinyl chloride (PVC), 0.5 weight percent polypropylene (PP) and 0.5 weight percent polystyrene (PS). In addition, the typical bale contains such additional contaminants as plastic film, dirt, paper, aluminum and other trash and the residue from contents of the crushed containers. Typically, the combined PET and HDPE contents of bales of crushed post-consumer containers will comprise 70 to 90% by weight of the bale.
Recycling of post consumer commingled rigid plastic containers also requires that commingled containers of different plastics be processible regardless of condition. Bales of these crushed containers derived from association with trash presents an appearance of a dirty mass of objects with some of the various colors of the different plastics present being muted by the presence of dirt and other trash. Nevertheless, the outgoing recycle plastic must have the appearance of quality, i.e., appear clean, shiny and pristine, and free of color contamination. It is no wonder that the article entitled "Plastics Recycling Gains Momentum", Chemical Engineering (Nov., 1990) states on page 39 as follows:
"Plastic recyclers use either mixed, commingled plastic streams--which are next to impossible to segregate economically [emphasis supplied]--or specify that only the pure stream be purchased."